Attaching Door Jamb to Sill

[zdorsch]

Opinions wanted!

Thank you all for answering my last post about exterior door frames--which was for a set of french doors.

This question is about constructing an entryway door set with jambs and sill. What is the general consensus for attaching the door jambs to the door sill--attache or not? I plan to order a aluminum sill and build the door jambs, but am unsure as to whether the sill should have screws running through it into the inner door jamb on each side (the jamb that actually surrounds the door itself)?

I am mimicking the set up that we have at work, single entry door and two side lites with a sloped sill, but cannot actually see how it was constructed. From what I can tell the outer side jambs appear to be attached to the side of the sill and the middle jambs appear to attached to the top of the sill.


Thank you!

 

[Gotcha6]

Exterior door units can be made either way, but most manufacturers attach the side jambs to the sill from the bottom. Wooden sills are rabbeted for the jamb and dadoed for the side light/door jamb. They are also step rabbeted laterally so that the sheathing will need to be cut away beneath the sill. Aluminum sills are usually flatter and can be set atop the subfloor but all vertical members are screwed from the bottom. You shouldn't try using the aluminum thresholds for this purpose as they are cut to go between the side jambs rather than under them. Their profiles aren't wide enough for this purpose either.

 

[junquecol]

The outer jambs are screwed into end of sill. The extrusion has holes to accept screws, but you have to be "dead on" with holes in jamb. Inner jambs are quite often stapled through sill. Very few high end door assemblies use aluminum sills. A white oak sill would be easier to use.

 

[SubGuy]

+1, been there!

The outer jambs are screwed into end of sill. The extrusion has holes to accept screws, but you have to be "dead on" with holes in jamb. Inner jambs are quite often stapled through sill. Very few high end door assemblies use aluminum sills. A white oak sill would be easier to use.

 

[zdorsch]

Thanks for all your replies!

Based on Denis and Bruce's comments I am leaning toward making a white oak sill. I was reluctant to construct the sill out of wood, but guess that since I already have the 8/4 white oak this would be a cheaper and more straight-forward option for me.

When using a wooden sill, would I then attach the door/side lite jamb by mortise and tenon? And then screw the outer jamb into the side of the sill?

Thanks,

Zach

 

[Gotcha6]

The side jambs need only be rabbeted or dadoed into the sill as required relative to their position. This rabbet or dado should be made square to the sill bottom regardless of any top taper you may design in & should stop before the outside edge of the sill even if it means notching back the jamb. Typically this means using a router or RAS setup. Sills usually protrude from the jamb stock 1-1/2 - 2" to receive brick mold. They are also longer than the outside jamb openings to allow for this as well.
Are we reinventing the wheel here?

 

[junquecol]

You will probably find a millwork shop that makes doors will sell you a length of sill stock for a lot less than it takes to make one.

 

[zdorsch]

Not so much trying to reinvent the wheel as to make sure that I build and the door jambs and sill the correct way. I have a better idea now after reading your post and seeing Townsend's explanation with pictures helped.

 

[zdorsch]

Bruce,

I thought about that, but I need a sill that is 60" wide to accommodate the door and two side lites. My thought is that its not too difficult to cut a slope on the front of the sill, so I think this is doable for me.

Thanks,

Zach

 

[junquecol]

Bruce,

I thought about that, but I need a sill that is 60" wide to accommodate the door and two side lites. My thought is that its not too difficult to cut a slope on the front of the sill, so I think this is doable for me.

Thanks,

Zach

Places like Stock, Capital City, etc will sell you any length you need, up to 12'.

 

[Gotcha6]

Bruce,

I thought about that, but I need a sill that is 60" wide to accommodate the door and two side lites. My thought is that its not too difficult to cut a slope on the front of the sill, so I think this is doable for me.

Thanks,

Zach

In addition to a front slope you will also need to cut the bottom rabbets to accommodate the subfloor and lip out beyond the sheathing. Look carefully at a wood sill in your carpentry book. It shows the subfloor and finish floor cut away to let the sill rest on the rim band joist. Most homes are sheathed all the way to the outside of the rim band and the sill is rabbeted away to set below the floor sheathing only outside the exterior vertical sheathing. This means possibly rabbeting the bottom a width of 4-1/2" to have the backside of the sill flush with the inside of the wall. Good luck....